dweste,

A good source of free strong (possibly rare earth) magnets is to open up old computer hard drives and remove the plate magnets housed inside. Old server drives are better, their magnets are much bigger and stronger.

As others have noted, they are both strong and can be fragile due to stresses from dropping them or accidently letting two of them jump together.

FYI When handling magnets, make sure that you DO NOT allow any of your skin to get caught between two magnets. A buddy at work that collects these magnets has several blood blisters from getting his fingers and parts of his hands pinched.

Regards,
Comanche7

Never opened a hard drive. What size range are these magnets? Can they be cut or otherwise re-sized?

Thanks.

They are maybe 1" wide, usually attached to a small metal plate. usually two, one above and below the swing arm that moves the head arm. They are very hard, dremel bits barely even scratch.

You might want to take a look at these:
http://www.tacticaltailor.com/magnamagsinglepistolmagpouch.aspx

Dweste,

Sizes vary from drive to drive, PC and laptop drives have smaller magnets, the larger server type drives have larger ones, ranging 1 to 2 inches across, slightly more than 1/16 inch thick and the width varies, I've seen a couple that were more than 5/8's of an inch on the third dimension.

They will generally have some curves or notches on them and resizing them is iffy at best. Mostly just by breaking them in my experience, not real accurate, but if you have enough you can generally break one the right size (eventually). Best bet is to use the flat angled glass breaker pliers (regular jaws that have small pieces of angle iron on them to hold the work piece with parallel grips).

Eugene's commment about the hardness is accurate.

Regards,
Comanche7